We were caught up in the HDR fad, and lamented how poor iPhoto is at managing photos meant to be grouped, as when auto-bracketing exposure or shooting for panorama stitching. As I said aloud that the problem seems to be there's a need for grouping items at a "less than album" manner, I recalled the original piles patent and lamented that they hadn't moved forward on that, and here's a perfect opportunity for them to actually innovate in user interface. I believe I went on to complain that if Tognazzini were still there they would've solved this problem already.
What makes this conversation memorable is the punchline: later that week I decided to look into Aperture and discovered that it has stacks. Exactly the feature we longed for. And it'd been there for a few months already.